My 2004 tralblazer a/c will blow out the floor when you put it on the dash vents why?

More than likely a bad vacuum or electric actuator, or bad vacuum line. Actuators control the mode doors to change from floor, vent, and defrost.

its either a bad air control panel or u have a bad damper valve in your dash

There are no vacuum lines, all of the air directions and movements are controlled by doors in the HVAC system, and these doors are driven by actuator motors. These parts sometimes wear out and require replacement, which can be a difficult job that involves taking the dash apart.

this vehicle has electronic acuators that move the doors and do not use vacuum. the mode door actuator is bad causing this problem. there is a defrost acuator that works the defrost position and a mode door that works floor/vent operation. the defrost moves and diverts airflow up defrost vwents this is why you can still have defrost and floor.

Sounds like it is going through the recalibration process. We run into this issue when replacing the batteries on these. In the underhood fuse block there is a HVAC fuse. Pull it, wait 30 seconds, put it back in, and turn the key to the run position. You should hear the vents moving around. wait for about a minute or so, do not touch anything. If the self test/calibration passes everything will return to normal. If after several attempts you can not get it to return to normal than there is a problem with the HVAC system that will need to be resolved.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

its a problem with the switching mechanism. you have to look up under the dash to see if you can see where the switching mechanism is. if you can not see it from there youll have to remove complete center dash

Hope I was avle to help, glad you up and going.

Is it a new vehicle? I had a new vehicle that had the same problem. Answer was that the holes weren't punched out of the vent.

ck for vaccum leaks at engine comparment small plastic lines

It may be the actuator not working properly. Should be above the accelerator pedal to the right.

Keeme